C/1956 R1 Arend-Roland
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Comet C/1956 R1 was discovered on 8 November 1956 by Sylvain Julien Victor Arend and Georges Roland (Royal Observatory, Uccle, Belgium), that is 5 months before its perihelion passage. Later, Sigeru Kaho (Tokyo Observatory, Konko Station, Japan) found an image of this comet on a plate he had exposed on 7 November 1956 during observations of variable stars. C/1956 R1 was observed until 11 April 1958 [Kronk, Cometography: Volume 4].
Comet had its closest approach to the Earth on 20 April 1957 (0.569 au), 12 days after its perihelion passage.
This is a comet with nongravitational effects strongly manifested in positional data fitting. Two NG solutions given here are based on data spanning over 0.602 yr in a range of heliocentric distances: 1.16 au – 0.778 au (perihelion) – 2.86 au; asymmetric NG solution was chosen as preffered orbit.
All solutions given here are based on data spanning over 1.42 yr in a range of heliocentric distances: 2.83 au – 0.316 au (perihelion) – 5.36 au.
This Oort spike comet suffers rather notable planetary perturbations during its passage through the planetary system; these perturbations lead to escape the comet from the planetary zone on a hyperbolic orbit (see future barycentric orbits).
See also Królikowska 2014 and Królikowska 2020.

solution description
number of observations 239
data interval 1956 11 08 – 1958 04 11
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 2.83 au – 0.32 au (perihelion) – 5.36 au
type of model of motion NT - non-gravitational orbits for asymmetric, standard g(r)
data weighting YES
number of residuals 458
RMS [arcseconds] 1.38
orbit quality class 1b
previous orbit statistics, both Galactic and stellar perturbations were taken into account
no. of returning VCs in the swarm 4943 *
no. of escaping VCs in the swarm 58
no. of hyperbolas among escaping VCs in the swarm 7
previous reciprocal semi-major axis [10-6 au-1] 42.96 – 76.37 – 110.14 R
previous perihelion distance [au] 0.23 – 0.3 – 510 R
previous aphelion distance [103 au] 18 – 26 – 46 R
time interval to previous perihelion [Myr] 0.86 – 1.5 – 3.5 R
percentage of VCs with qprev < 1081
percentage of VCs with 10 < qprev < 201
percentage of VCs with qprev > 2018
Time distribution of positional observations with corresponding heliocentric (red curve) and geocentric (green curve) distance at which they were taken. The horizontal dotted line shows the perihelion distance for a given comet whereas vertical dotted line — the moment of perihelion passage.
previous orbit statistics, here only the Galactic tide has been included
no. of returning VCs in the swarm 4944 *
no. of escaping VCs in the swarm 57
no. of hyperbolas among escaping VCs in the swarm 7
previous reciprocal semi-major axis [10-6 au-1] 43.30 – 76.35 – 110.15 R
previous perihelion distance [au] 0.19 – 0.28 – 0.31 R
previous aphelion distance [103 au] 18 – 26 – 46 R
time interval to previous perihelion [Myr] 0.86 – 1.5 – 3.5 R
percentage of VCs with qprev < 1098
percentage of VCs with 10 < qprev < 201
percentage of VCs with qprev > 201